Instructables

Homopolar Motor With Five Speed Manual Stick-Shift

video Homopolar Motor With Five Speed Manual Stick-Shift

This video show how to build a homopolar motor that's really different...it's got a five-speed shifter!

The homopolar motor is the simplest design electrical motor in the world. It uses a battery, a neodymium magnet and a wire. Usually, either the copper wire or the magnet rotates. In this case the battery rotates.

Here, I've used a battery, a neo magnet, and a copper wire wrapped around a coat-hanger. The coat-hanger acts as both electrical connection and support for the hanging battery. Coins are used to change speeds of the rotating "battery-plus-change" motor.

I've been recently told that US coins, being non-magnetic, won't work for this Instructable. (Sorry about that!) Perhaps the US coins could be glued together to make it work. Furthermore, some Canadian pennies are magnetic and some are not.

You can order the BEST neodymium super-magnets from K&J Magnetics here.

See more of my homopolar motor videos at :
http://ca.youtube.com/MrfixitRick
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swagramp5 months ago

You can actually use pennies dated before 1981 (thats when they switched over to the zinc alloy).

IshBarrett11 months ago
Thanks a lot.
IshBarrett11 months ago
Can any coins which are made of steel, be used to make this motor work?
mrfixitrick (author)  IshBarrett11 months ago
Yes, steel coins or steel washers will work.
pablopsz2 years ago
I liked his creation, really.

In this video you can see a micro motor homopolar:

http://www.youtube.com/watch?v=F4fI0MAu1Vs

Greetings and congratulations
mrfixitrick (author)  pablopsz2 years ago
I like your "cute" motor creation as well...nice work!
vruiz32 years ago
unexplained things #2 homopolar motor with 5 speed shft. :P
your idea is a wonderful and revolutionary idea ,sir
Sky_line913 years ago
do you happen to know if this is possible with wires coming from a power source instead of a battery?
mrfixitrick (author)  Sky_line913 years ago
A dc power source will work. It will require up to 5 amps at a couple of volts.
awesome, thanks
 how does the movemement of the shifter result in the variation in the speed
mrfixitrick (author)  divyanshu0074 years ago
 The shifter gets moved from coin to coin. Although the various coins have different resistances and magnetic values, the radius of contact of the shifter conductor to the spinning magnetic field is the biggest speed factor. (as long as the conducting coins don't have too much resistance).

Generally, the larger radius coins will spin slower but with more torque. This torque and speed could be calculated using the Lorentz force principles.
would it be possible to just stack different thickness and diameters of the neo mags and apply the gear theory to thus?
mrfixitrick (author)  Rottom3 years ago
Yes, that should work, and produce more torque and rpm as well.
I'm guessing that using any circular magnetic surface like one having a conical cross-section would actually give you a variable rate transmission. No more fixed speed shifts. Simply sliding the shifter from one radius to another would immediately change the speed of the device without ever having a discontinuation in rotation.

Xavian-Anderson Macpherson
ShingoshiDao
Come to think of it. A sewing thimble would work perfectly for testing the idea. Because the less variation in mass, the more accurately one can view the effect of changing the radius alone has. I would flip the cone of the thimble to cover the end of the magnet and extend over the battery. The result will be more stability avoiding the necessity to align coins for proper rotation.

ShingoshiDao
mrfixitrick (author)  Shingoshi4 years ago
 Good idea, I will have to try it one day...or perhaps you should? hehe
I just need to find myself some small NbFeB magnets. I'm thinking of a few devices around my house that I could strip apart to acquire the magnets from. So if I do get to do it, I'll definitely post my results here and elsewhere (ie. You Tube).

ShingoshiDao
mrfixitrick (author)  Shingoshi4 years ago
 Interesting concept...A fixed power but variable speed motor with a cone-shaped commutator.
I am doing this for a science project... somewhat. I am having trouble getting it to work. The thing i dont understand is the coin part. Do you need coins or magnets or both?
mrfixitrick (author)  J_gilbert69113 years ago
The coins are magnetic Canadian coins. They are not necessary, except as a means of altering the speed. (different radius coins)

The magnet is necessary, and must be a powerful neodymium type magnet, found at a place like K& J Magnetics.
Would this type work? 13/16" dia. x 1/16" thick Grade N42 - Nickel Plated
mrfixitrick (author)  J_gilbert69113 years ago
This experiment is tough to do. That 13/16" magnet won't work.

I just tried a 3/4" x 1/16" and it would not hold. 3 or 4 of them stacked will likely work.

A 1/2" x 1/4" N52 magnet will work. I prefer a stronger N52 magnet, and definitely thicker than 1/16", at least 3/8" thickness.

You could stack magnets like coins as well. For example, use a 1", then the 13/16" x 1/16", then a 5/8", 1/2", etc. stacked.
I bought a pack of 10 from K&J Magnetics. Would using several work?
mrfixitrick (author)  J_gilbert69113 years ago
Try an experiment with loading up the battery with as many stacked 13/16" magnets as it can take and still stick well on the hanger.
Then remove one or two magnets for a little less weight. The coins are optional to vary the speed.

The hanger tip where the battery hangs is somewhat critical. It must be rounded and smooth, not a sharp point or edge. The magnetized battery hangs in better that way.

A thicker wire coat-hanger will work better than a thin wire one.
I went to the local home-depot and just gor regular copper-wire. Bought a few D batteries. Then from my science teacher i got a 2", believe its a black hole magnet (like refrigerator magnets but bigger and with a hole in the middle) I wrapped the magnet in tin foil and shaped the wire to fit around it. IT WORKS!!! IT WORKS!!! lol :) So far i have made the heart shape and somewhat of a spiral. Anyone with any ideas for other cool shapes??
mrfixitrick (author)  J_gilbert69113 years ago
Good idea!
I didn't think that would work!

Have a look at this movie that shows wire-formed dragonflies and butterflies using the homopolar motor idea.
camaroboy4 years ago
how much torque does 1st gear have?
mrfixitrick (author)  camaroboy4 years ago
 Good question. I don't know. 
camaroboy4 years ago
why does the battery spin faster when the wire touches the coin closest to the magnet/battery?
mrfixitrick (author)  camaroboy4 years ago
 The magnetic field is stronger when closer to the magnet.
 And the radius is smaller, making it run faster.
camaroboy4 years ago
how come mine doesnt work properly? it only works when touching the magnet. seriously, whats wrong with mine?????????
mrfixitrick (author)  camaroboy4 years ago
 The magnet may need to be stronger.

The coins work best if they are magnetic like Canadian coins or magnetic coins from a magic shop.
camaroboy4 years ago
how many rpm can the 5 th speed do? 
mrfixitrick (author)  camaroboy4 years ago
5th is about 500 rpm.
camaroboy4 years ago
omg this things awesome. im doing it for my science project, and im gonna burn it to the ground. lol just kidding. again great project and keep up the good work.
ToastaG4 years ago
The shifter reminds me of a record player.
ok no-one has asked a question about the use of the battery, does the batteries contents act as a magnet or fly-weight or both? would using a larger battery produce a faster motor or more torque etc? im really interested in this odd motor. thanks,simon.
mrfixitrick (author)  finlandrocks6 years ago
Good question! The battery acts as a magnet in that when it is attached to a magnet, it's steel core gets magnetized and enables it to hang off the wire-frame holder. It also acts as a flywheel somewhat. The current in the battery determines the torque and the voltage, the speed. I've been using the rechargeable AA Duracell NiMHbattery in the 2650 mah size. It's fun..try it for yourself
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